Vyper

Non-breaking changes and improvements:

- Add the ``abs`` builtin function ([2356](https://github.com/vyperlang/vyper/pull/2356))
- Streamline the location of arrays within storage ([2361](https://github.com/vyperlang/vyper/pull/2361))

This release fixes a memory corruption bug 2345 that was introduced in the `v0.2.x` series and was not fixed in [VVE-2020-0004](https://github.com/vyperlang/vyper/security/advisories/GHSA-2r3x-4mrv-mcxf). Read about it further in [VVE-2021-0001](https://github.com/vyperlang/vyper/security/advisories/GHSA-22wc-c9wj-6q2v).

Non-breaking changes and improvements:

- Optimize ``calldataload`` (2352)
- Add the ``int256`` signed integer type (2351)
- EIP2929 opcode repricing and Berlin support (2350)
- Add ``msg.data`` environment variable 2343 (2343)
- Full support for Python 3.9 (2233)

This is a patch release to fix a memory corruption bug that was introduced in v0.2.9 (2321) with excessive memory deallocation when releasing internal variables

This is a quick patch release to fix incorrect generated ABIs that was introduced in v0.2.9 (2311) where storage variable getters were incorrectly marked as `nonpayable` instead of `view`